It is well recognized that water for drinking purposes must be relatively pure to avoid health problems. It is also well known from medical and other scientific studies that health is improved and maintained by drinking water from which undesirable salts and minerals have been removed. Water purification units, now on the market for use in households, utilize active carbon (e.g. charcoal) both as a filter and an adsorbent to remove impurities. Although charcoal will serve to remove by filtration particles suspended in the water and adsorb odoriferous materials contained in the water, the charcoal is of practically no use in removing most ionic substances (e.g. various salts) dissolved in the water.
Other means for purifying water involve use of reverse osmosis, as shown and described, for example, in U.S. Pat. Nos. 3,505,215; 3,746,640; 4,083,780; 4,156,621; 4,161,445 and 4,206,048, and ionic exchange resins, as shown and described, for example, in U.S. Pat. Nos. 3,431,201; 3,928,192; 4,083,782; 4,200,695; 4,219,414; 4,302,548; 4,334,949 and 4,349,442. Some of these patents, e.g., U.S. Pat. Nos. 3,431,201; 4,161,445 and 4,206,408 show use in combination of reverse osmosis and ion exchange to purify water.
The systems described in the above-mentioned patents are designed for large scale use and usually require an external source of power, such as electricity, to pump the water through the system. These systems are not only very sophisticated but are expensive to construct and operate making them unsuitable for small scale use in households.